The grapefruit-size, frosted-glass orb sits quietly on a desk, calling out to be caressed. Passersby invariably stop to touch it. They also ask why its light glows citrus green and flashes intermittently. The reason: The temperature outside has been hovering in the sixties, and it is one of the rainiest seasons on record in New York City. The orb’s color, which changes with the weather, ranges from ice-cold blue to temperate green to fiery-hot red. The flashing signifies precipitation.

Beaming in the weather forecast is just one of many tasks the Ambient Orb can perform. Designed to distill a complex influx of information into an easily observable form, the softly shining ovoid can also track the stock market, local pollen levels, traffic jams, and, if specifically programmed, your grandma’s glucose or a favorite baseball player’s batting average. Computers at Ambient Devices, the parent company, monitor a wide variety of data, crunching each down into a linear scale that reflects up-to-the-minute changes and is wirelessly transmitted to individual orbs. Each orb user can register a preference for a particular data set through the company Web site.

David Rose, the CEO of Ambient Devices, says that the Orb is aimed at those overwhelmed by a constant barrage of information. Instead of compulsively checking the Dow-Jones average, say, Orb users can be soothed by a steady but dynamic signal that can be absorbed with an occasional glance. The light glows red if the Dow has fallen, green if it has gone up, and it flashes if it crosses a threshold. One fan of the market-tracking function is Stephen Petranek, Discover’s editor in chief, who borrowed the Orb one day to test it. Now he won’t give it back.

An ordinary bottle, as everyone knows, has an inside and an outside. But a Klein Bottle, conceived by the German mathematician Felix Klein in 1882, consists of a single continuous surface, similar to a Möbius strip. If you walked along its surface, you wouldn't experience anything other than a flat road, although you’d pass seamlessly from the inside to the outside and back again.

Photograph by Jens Mortensen

The Klein Bottles, at left, measure seven to four-and-a-half inches high. You can swig beer from the Klein stein mug,

at right.

Since its conception, the idea of the Klein Bottle has held a special fascination for mathematicians, but no one had actually ventured to make one out of glass until 1997. That year, Cliff Stoll, an enterprising astrophysicist, decided to manufacture and market this topological marvel—or, rather, an approximation of one, since the real thing can exist only in the non-Euclidean realm of four spatial dimensions. Stoll hired a glassblower and gave him precise instructions: Cut a small hole in the bottom of a Pyrex flask; stretch the neck of the flask upward, then curve it so that it pierces back through the side of the bottle and connects to the hole in the bottom. Stoll took his finished product into the University of California at Berkeley math department, where a mathematician recognized it immediately and exclaimed, “I want one!” After a second bottle got snapped up, Acme Klein Bottle Inc. was born.

Before starting Acme, Stoll was best known for having spent one year tracking down a notorious computer hacker in the 1980s, then chronicling his pursuit in a best-selling book, The Cuckoo’s Egg. Now, however, he spends large chunks of his time peddling bottles at American Math Society meetings and expanding his inventory. Besides the basic Klein Bottle, Acme now also sells small Klein beer steins (ein kleines Klein Stein, in German), as well as knit wool Klein hats and matching Möbius scarves in cheerful colors. “I have a tighter monopoly than Bill Gates,” jokes Stoll, “and a better market share than Cisco.”

The Olympus Mic-D digital microscope turns amateur microscopy on its head. The main lens of the Mic-D points up, not down, and an LED attached to an ingenious rotating arm can be set to project light on a specimen from almost any angle. Best of all, the Mic-D plugs into your computer, so the microscopic images pop up on the monitor. You can record these images as digital photos, then crop them, change their light

Photography courtesy of Olympus

properties, and add text. You can even document something that changes over time— say, organisms swimming in a drop of pond scum— by imaging the specimen in real time and creating a digital movie, The Mic-D software package includes user- friendly tutorials and a digital library of specimen images.

The magnification power of the Mic-D, which can show specimens at up to 255 times their actual size, is less than many classroom microscopes. But the Mic-D will dramatically expand your view of an unseen world because you don’t need to fit every specimen onto slides or use slide covers. I immediately began scouring my office for objects to scrutinize— a CD, the hands of my watch, even salt crystals that looked like gigantic white cubes when magnified. [For a significantly cheaper, conventional microscope, try the $138 National Model 109-L, a sturdy beginner scope suitable for kids but good enough that adults can enjoy it too.]

The Roomba FloorVac from iRobot, a squat disk about 12 inches in diameter, scuttles across the carpet like some Precambrian pet, ingesting crumbs and dirt as it navigates walls, circles chair legs, and crisscrosses the room. Roomba operates autonomously, leaves the carpet

Photograph courtesy of iRobot

remarkably clean, and when the job is done, stops and shuts itself off.

The robotic vacuum cleaner is not a new idea, but Roomba is the first commercially available model that’s truly affordable and simple to use. There’s no programming; you just turn it on and let it go. A bump sensor tells the machine when it has reached an obstacle, and infrared sensors guide it along walls and prevent it from tumbling down stairs. If the Roomba gets stuck on a household object, it automatically switches off, then beeps for help.

Although the Roomba uses only 30 watts to do its job—a typical vacuum consumes 1,000 watts—its actual air velocity at carpet level is comparable to a conventional vacuum cleaner’s. One drawback, however, is its small dirt capacity: The particle bin and dust filter must be emptied after each use. Still, the Roomba serves as an efficient and genial ambassador for robot-kind. That’s good news for its manufacturer, iRobot, which is hard at work developing other robots for everyday use.

— Fenella Saunders

The Telescopes

Celestron NexStar 60GT, $299

Orion SkyQuest XT8 IntelliScope $479

Galileo revolutionized astronomy with little more than a three-foot-long wooden tube and a pair of 1.5-inch-wide glass lenses. Four centuries later, amateur stargazers can choose from a variety of sophisticated home telescopes offering a sharp and expansive view of the universe that would have made Galileo’s jaw drop.

Celestron’s NexStar 60GT is a refracting telescope similar to the one used by Galileo. But the NexStar comes loaded with what 21st-century astronomers call go-to technology: software-controlled drivers that can automatically focus the viewfinder on 4,000 preprogrammed celestial objects, including galaxies, nebulas, and star clusters. You first have to orient the telescope, either by punching in your location and time or by pointing the telescope at two known stars so it can triangulate its position. With a main lens that is just 2.4 inches wide, the NexStar 60GT gathers roughly 10 times as much light as Galileo’s crude instrument but lacks the power to zoom in closely on many of the distant objects in its catalog. Still, the relatively low price and ease of assembly of the telescope will appeal to amateurs in quest of striking views of the moon and planets. [Meade Instruments Corporation sells the Meade NGC-60, a similar telescope with a less sophisticated computer control, for $189.99]

Orion's SkyQuest XT8, a reflector telescope with an 8-inch mirror, offers far brighter and crisper views than the NexStar 60GT for not much more money. The SkyQuest XT8 is relatively bulky but it is easy to assemble and operate. Beginning astronomers using the original XT8 needed to consult star charts to help them locate the objects they wanted to see, but that version has now been replaced with the SkyQuest XT8 IntelliScope, which has a computer controller analogous to the go-to control on the Celestron. A simple glance into the heavens through the SkyQuest XT8 provides high-resolution views of such wondrous celestial objects as multiple stars, Jupiter’s colorful cloud bands, bright nebulas, and sparkling globular star clusters. Galileo would have been delighted.

— Maia Weinstock

MODELS & KITS

*Model Airplanes

Sean Kinkade, ParkHawk, $199

Ornithopter Technologies, Swallow, $15

Spectra Star, Fearsome Flyers, $6.99

Tedco, Batwing and Butterfly, $11.99

Photograph by Jens Mortensen

To best test ParkHawk’s prowess, you’ll need to find a space the size of a football field.

In 1485 Leonardo da Vinci made detailed sketches for a human-powered ornithopter: a contraption designed to mimic bird flight. His wing-flapping device never left the ground, but half a millennium later, flight enthusiasts can choose from a variety of model ornithopters powered by everything from rubber bands to diesel fuel. One of the more impressive designs is the new battery-powered, radio-controlled ParkHawk (for information, write to thopter@earthlink.net). The raptorlike ornithopter, which features a four-foot wingspan, ripstop nylon wings, motor, and fiberglass frame, comes unassembled; the servos and radio receiver required to control its flight must be purchased separately. Once in the air, the ParkHawk can climb overhead to a height of 250 feet and fly 20 miles per hour. The graceful Swallow, from Ornithopter Technologies (www.ornitech.com), is a delicate balsa-wood and tissue-paper creation with a 20-inch wingspan; it requires a few hours to assemble and is powered by a supercoiled rubber-band motor. Spectra Star’s preassembled Fearsome Flyers (mvazquez@spectrastar.toybiz.com), shaped like dragonflies, pterodactyls, and other airborne beasts, have Mylar wings and a rubber-band motor that’s wound with a simple cord. They’re noisy, low-altitude fliers but fun to watch. Tedco’s (www.tedcotoys.com) fliers are as gentle as moths in flight and even simpler in design: Their rubber motors are twisted with a crank, and each bat or butterfly model comes with background about the animal it resembles.

— Lauren Gravitz

*Model Rockets

Micro Maxx, $16.99

Estes Astrocam, $29.99

Estes Max Trax, $39.99

Amateur rocketeers once spent hours building backyard missiles from scratch. But these days anyone with limited launch space and a hankering to reach for the sky can choose from an array of ready-to-fly model rockets that offer the authentic thrill of ignition, launch, and

Photograph by

Jens Mortensen

liftoff to impressive heights. Quest’s Micro Maxx is 3 1/2 to 5 1/2 inches long, easy to set up, and reaches an altitude of 100 feet powered by the smallest rocket engine on the market: On a scale that rates motors from size A to O—according to magnitude of power—the engine is rated 1/8 A. Launching the Micro Maxx is virtually foolproof. Just plug the cylindrical engine into the tail of the rocket, then hook up the igniter wire, which attaches to a battery-powered controller that's operated from a safe distance of about 15 feet. Once you press the launch button, electricity combusts a solid propellant, made mostly of potassium nitrate, generating a hot thrust of gas that shoots out from the bottom of the rocket. During flight, a second charge in the engine automatically blows off the nose cone to release a Mylar streamer (other models use parachutes). After the rocket floats down to earth, you can plug in one of the replacement engines supplied with the kit. Should you harbor loftier ambitions, try the Estes Astrocam (www.estesrockets.com), which is 18 inches long, uses a C engine, and has a film camera in its nose cone that snaps an aerial picture at the rocket's apogee. Once launched, the Astrocam can reach an altitude of 500 feet, where it’s barely visible. The Estes Max Traxx, also powered by a C engine, offers an alternative novelty: a built-in altimeter that allows you to record for posterity the rocket’s peak altitude.

The Stirling engine has been the next big thing since 1816, when the Scottish clergyman Robert Stirling built an energy-producing contraption that he hoped would supplant the steam engine, the industrial workhorse of his era. The Stirling is an air-compression engine that emits no exhaust and will happily crank out energy from virtually any external heat source.

When placed on top of a steaming beverage, the easy-to-assemble MM-5 Coffee Cup Engine Kit will harness enough waste heat to spin a fan for about 10 minutes. The engineering principle is simple. Heat from the cup of coffee causes the air in a compression shaft to expand, pushing a piston that turns a crankshaft, which in turn spins a propeller. The process can be reversed by placing the engine on, say, a bag of frozen peas. The relatively hot air in the top of the compression shaft will push the piston down, turning the crankshaft and propeller in the opposite direction.

While watching the MM-5 engine’s fan whir, you can contemplate the coming Stirling revolution. New friction-reducing seals and materials that contain light gases at high pressures could transform this relic into a modern powerhouse. In fall 2002, inventor Dean Kamen announced that the next generation of the Segway, a two-wheeled personal transporter that mimics the body’s balancing ability, will be powered by a Stirling engine.

In 1920 a Russian engineer named Léon Thérémin invented an instrument like none that came before. The thereminvox or theremin was the world’s first electronic instrument and the only one that could be played without being touched. Inside it were radio tubes that produced oscillations at two sound-wave frequencies beyond the range of the human ear; together, they produced an audible signal. To change the pitch, a player waved one hand toward or away from a vertical antenna on the right. Waving the other hand around a horizontal loop on the left adjusted the volume.

The instrument was an instant success, and avant-garde orchestras rushed to embrace its unearthly sound, a cross between a violin’s rich tone and the squeal of loudspeaker feedback. Even after its inventor disappeared into the Soviet gulag in 1938, the theremin could still be heard swooping through many 1950s sci-fi movie sound tracks and even in the Beach Boys’ 1967 hit “Good Vibrations.”

Now the theremin is undergoing a small renaissance among musicians, in part due to the availability of inexpensive build-your-own kits. The best-regarded of these is the PAiA Theremax, which replaces the original’s vacuum tubes with an integrated circuit board. This makes the instrument smaller, cheaper, and easy to build. The Theremax also incorporates an output port that can send the sound to a computer, allowing players to modify the signal to produce variations weirder than even Léon Thérémin could have ever dreamed. Rachmaninoff may be out of reach for most, but the Theremax is fine for rock, blues, and jazz, or any genre in which being precisely in tune is not strictly necessary. It’s also a spectacular conversation piece. Those who have heard the strange history of the theremin will soon be eagerly contorting their arms in a wild attempt to play it themselves.

Even the simplest-looking apparatus can turn out to be surprisingly complex. The AirZooka is just a big, brightly colored plastic barrel, a little narrower at the front, with a loose plastic sheet attached to a pair of elastic cords at the back. Pull back on the sheet, let it go, and—whump!—you’ve fired a (harmless) 60-mile-per-hour blast of air at an unwitting bystander 20 feet away.

Simple, unless you’re the target. You were just hit by something that wasn’t just wind but wasn’t entirely solid either. Yet after traveling a fair distance, it still felt compact. The directions on the box say it’s a ball of air, but how do you make a ball out of air? And why should it hold together for any distance at all? Herb Tranthum, one of the engineers who designed the AirZooka, explains it this way: When you fire an AirZooka, a high-pressure shock wave leaves the toy first, quickly followed by an air ball. The shock wave creates a vortex of swirling air in its wake, which keeps the air ball intact and in place. If you’ve pulled the plastic sheet back just right, the ball threads the spinning ring of air and carries it on to your target. If your shooting angle is a bit off, however, you shoot a ring of air, not an air ball—though it feels the same to your target.

The physics of this device—involving the Bernoulli effect, toroidal vortices, and other such phenomena—is so intriguing that teachers may be using the AirZooka for their classroom demonstrations. But the wacky pleasure of shooting air balls requires, fortunately, no advanced degree.

Wanna drag? Clear a path for Blurzz, the racer propelled by a bang from its butt. This 12-inch-long rocket-powered car can reach a speed of 20 miles per hour; scale up to the length of a full-size drag racer and that's the equivalent of 500 miles per hour. Setup requires a 90-foot-long smooth track surface, such as an outdoor basketball court. Blurzz hooks onto a wire guide, which stretches from start to finish and keeps the car from careering off course. A pair of thin battery-powered wires inserted into the back of the disposable, 1 3/4-inch-long cylindrical engine ignites the solid gray potassium nitrate-based propellant, causing smoke and flames to shoot out the rear and forcing the mini dragster to blast forward. After traveling about 60 feet, Blurzz picks up a drag chute attached to the wire guide and then jolts to a stop on a plastic bumper. The explosive run is over in just five seconds, but insert a new engine and Blurzz is ready to go again. Unlike a flying rocket, it won’t shoot out of sight—or get stuck in any surrounding trees.

— Fenella Saunders

*Gliders

Xstream, Ultra Xstream, and Mini Xstream, $4.99-$19.99

Wow Wee Power Air Surfer: $49.99

Photograph by Jens Mortensen

The IWA on the Xstream Glider's nose stands for Internal Wing Aircraft, a technology that generates impressive lift and thrust as air moves through the duct-shaped wings.

If you’re the type who enjoys launching a paper airplane and watching how it bobs and weaves in the wind, you'll be blown away by the latest generation of toy gliders. The wing design of the Xstream Glider (www.iwatoyco.com) is so innovative that its pilot-inventor, Robert Carr, has received inquiries about possible military applications for an engine-powered version. The glider features three wings on each side of its fuselage, parallel surfaces that converge at the wing tips and dramatically increase the mass and velocity of airflow operating on those surfaces. The design has an astonishing effect on the glider’s lift and thrust. A flick of the wrist can send the Xstream a distance of 60 yards and to a height of 75 feet. The Power Air Surfer, a radio-controlled bi-wing glider produced by Wow Wee (www.wowwee.com), comes with a remote control, a rechargeable battery, and an in-field recharger. The Power Air Surfer glider needs its motor to gain altitude, but at 40 feet you can cut the engines and watch the plane glide gracefully to earth.

—Hannah Hoag

*Soccer Bots

Soccer Jr., $44.95,

Soccer Pro, $44.95,

AIBO ERS 31L, $599

Photograph by Jens Mortensen

Soccer Jr. uses three motors

and 17 gears to move its feet

and paddle. There is no

gearing for headers.

Last year, robotics aficionados used the occasion of the world cup soccer tournament to once again stage a special sideshow: RoboCup. The international competition, held in Fukuoka, Japan, featured teams of soccer robots in various shapes and ranging in height from 9 to 32 inches. The goal of RoboCup is to push the pace of robot evolution. But some new off-the-shelf kits will allow you to experience the challenges and triumphs of robotic soccer without leaving home. Two soccer robots from OWI (www.owirobot.com) can each be assembled with relative ease in a couple of hours and then set into motion using a handheld wired control device. The six-inch-long Soccer Jr. lurches along on six legs and uses a spinning paddle to scoop in the ball and then fling it about six inches away. The five-inch-long wheeled Soccer Pro is faster and more maneuverable, but its two vertical, parallel rollers that pull the ball into a central cavity, then spin outward to kick it, are less powerful than the Jr.’s paddle. Sony’s AIBO ERS 31L (www.aibo.com) is a much more elaborate robot, a cousin of the soccer dogs that actually compete in one RoboCup league. A sophisticated onboard artificial intelligence program lets AIBO respond to voice commands. In addition, a camera mounted in the mouth and a distance sensor in the nose help it detect a three-inch bright-pink ball. If you tell AIBO to “kick the ball,” microphones in its ears pick up the command, and a little light protruding from its head shines white. If it shoves the ball with its front foot, and you say “Good AIBO!” and press down gently on its head, the light glows green. AIBO will only nudge the ball with its head at first, then gradually learn to use its foot to kick. But be warned: Occasionally, this four-legged robot ignores commands altogether until you shake its paw or pet it.

Under pressure? Feeling tense? You’re not alone; every cell in your body is experiencing the same thing. While the man-made world is built using either tension (for example, suspension bridges) or compression (brick walls), the biological architecture of our cells uses a combination of both called tensegrity. Architect Buckminster Fuller coined the term tensegrity, short for “tensional integrity,” to describe a method he

Photograph courtesy of Design Science Toys.

Experimenting with the force of "tensional integrity"—and

with Tensegritoy—yields this octahedron.

developed for constructing surprisingly strong and flexible buildings that seem to float in space. Fuller got the idea from sculptor Kenneth Snelson, who was the first to use this principle in his work. His tensegrity sculptures look like three-dimensional exploded diagrams built of metal poles and tensioned wire: beautiful to look at, but a cold and distant beauty.

Now Design Science Toys offers Tensegritoy—tensegrity you can get your hands on. The materials themselves are simple: wooden struts, elastic cords, and plastic caps to keep things in place. The clever bit is the system of notches and holes in the struts that allow the cords to be strung with the appropriate tensions for various needs.

The set comes with detailed instructions for building three basic structures—a tetrahedron, an octahedron, and an icosahedron. (Alas, guidelines for creating many other polyhedrons are hopelessly abbreviated and opaque.) An octahedron displayed on your office desk is a guaranteed conversation starter. The materials are flexible and durable enough that you can playfully squash one of your creations or bounce it around the room, and a 31-page booklet gives plenty of background on the underlying science. So when your sculpture flexes right back into shape, you'll know just what principles of tensegrity you've demonstrated.

—William Jacobs

*The Tops

The Blizzard, $13

Bearing King, $15.99

DT TopDog, $28

The simple gyroscopic motion of toy tops has been a source of hypnotic appeal since time immemorial. But the latest tops are a far cry from the small clay cylinders that mesmerized children in ancient Rome and Greece. Old-fashioned string-wound peg tops tricked out with independently rotating tips are the rage with the skateboard-and-dirt-bike crowd. Duncan Toys representative Steve Brown, a competitive spinner, can release a top, snare its tip back on the string, twirl the top over his head, slide it in a spiral down his arm, and then continue

Photograph courtesy of Duncan Toys

spinning it in his hand. Tricks in the hand are better done with a ball bearing-equipped top, where the tip stays put while the top spins. “That reduces friction and adds a ton of spin time in your hand,”says Brown. Aspiring stunt spinners can experiment with the Spintastics Blizzard (www.spintastics.com), the Duncan Bearing King (www.yo-yo.com). Duncan’s cool line of Tetra tops (including the Executive Tetra, Octa, Icosa, and Cube, $16.99), which look like marbles glued together, spin on multiple axes. YoYoJam (www.yoyojam.com) has the DT TopDog($28), specially shaped to have ball bearing points at both ends to really let you flip the top around.

Egged on by the super tricks in Duncan’s “How to be a Player” video ($17), and Spintastics’ “Spinology” instruction video ($15), I talked Brown into giving me a personal lesson at New York’s Toy Fair. He showed me how to hold one end of a 60-inch-long string at the wide part of the top, then hook it around the tip and wind it tightly around the body of the top. A plastic “button” on this end of the string slips between two fingers. He explained that I had to keep the tip pointing straight up as I threw it, as the action of the string popping off the tip flips the top over 180 degrees. But the button came out of my hand and the whole thing landed in a tangled heap on the floor. Brown put his hands on his hips and looked at it, then peered at me in mock disgust. He scooped up the top, wound it again, and handed it back to me. This time I managed to hold the string and get the top spinning, but it wobbled uncontrollably. Brown was encouraging — he told me I just had to follow through on my throw more.

Brown says his unofficial record for keeping a top spinning is three hours, but that’s done by using the string to regenerate the spin on the top. “Actually the peg top is poorly designed to spin well because all the weight is up high,” says Don Olney, founder of The Toycrafter, a toy store that specializes in tops, and owner of about 7000 tops. Olney has come up with some alternate top games. Swirl-Arounds ($5.50) and MagneTops ($5.00) from The Toycrafter (www.toycrafter.com) have a magnetic tip, so they can be suspended upside-down from a metal object, such as a bent paperclip, and spun gently. Tilt the paperclip slightly and the tops will follow its labyrinthine twists without running off the end. The A Maze ’N’ Tops ($8.25) have a small plastic top that has to be guided through the cut-out path of a maze on a wooden board before it runs out of spin.